Field of the Invention
The present invention relates to an apparatus for commercially producing large quantities of fish and aquatic organisms. The apparatus generates a microbial biomass from the degradation of harvested plant material and nutrient substrates, and uses this microbial biomass to generate and provide food for the fish and aquatic organisms, and to treat the wastes produced by the fish and aquatic organisms.
Description of the Related Art
The seafood industry is facing a growing crisis. The capture of fish from the ocean has peaked but the demand for fish continues to rise. Approximately, 75% of the world's fishing grounds are fully exploited, over exploited, or severely depleted. Over 90% of the large fish in the ocean have been harvested and may never be regained. The most desirable wild fisheries are collapsing, and many depleted species might never recover because their habitat has been destroyed or too few survivors remain to successfully reproduce.
Many feel that aquaculture is the only sustainable method for supplying fish to the world's population. Currently almost half of all food fish for human consumption is produced by aquaculture. In order to maintain the current level of global per capita fish consumption and given the likelihood of stagnant harvests from capture fisheries, it will be necessary for aquaculture to provide a much greater share of the food fish supply in the future.
However; aquaculture itself is facing a number of critical issues. Current aquaculture practices rely heavily on fishmeal and grain for feed. Because of this aquaculture is simply recycling existing food sources and is not itself a source of new food. Because the largest single production cost in aquaculture is for feed, the dependence on grain supplies means that feed could become disproportionately expensive with increases in grain and energy prices. In addition, by relying heavily on fishmeal and oil as substantial ingredients in fish feeds, aquaculture is contributing to overfishing and this will jeopardize the future availability of fishmeal and fish oil.
The grain and fishmeal that constitute aquaculture feeds may also be a significant source of contamination (pesticides, heavy metals, etc.) in fish because of bioaccumulation. The steadily increasing pollution of the world's oceans is reaching a point where it is now threatening the entire marine food supply chain. The contamination caused by oil, nutrients, sewage, and toxic chemicals has been well documented in the past, but these threats may soon be eclipsed by an even greater danger, that of plastic. The oceans now contain six times more plastic than plankton, which is the basis of the marine food chain. Furthermore, as the plastic is broken down into smaller and smaller particles it is entering the food chain itself. The health risk which this may pose is at present unknown. However, given the asbestos experience, there is serious concern that small molecular weight plastic (plastic bits) contamination could eventually become incorporated into biological cellular structures thereby making all ocean produced seafood and seafood products unfit for human consumption in the future.
In addition to these factors, many aquaculture operations themselves are contributing to the environmental pollution of the world's waters. Most current aquaculture systems are either flow-through systems or they are systems embedded in cages within large bodies of water (lakes, streams, and oceans). Consequently the nutrient and organic wastes discharged by these systems accounts for an increasing build-up of anoxic sediments and the nutrient pollution and eutrophication of lakes and coastal zones. Changes in oxygen, temperature, pH, suspended solids, ammonia, organic nitrogen, and phosphorus are often measurable downstream from hatcheries. This again increases the environmental problems and further threatens long term sustainable future production.
Phosphorus and nitrogen in farm wastes primarily originate from feeds and are of greatest concern due to their role in nutrient enrichment (eutrophication). Eutrophication occurs when natural waters receive excess quantities of nutrients which often results in blooms of noxious algae or excessive growth of higher plants. When the plants die, the decaying organic material can deplete water of oxygen to a degree detrimental to other aquatic organisms. This often results in fish kills and a serious impairment of the aquatic environment.
The primary sources of aquaculture wastes are from fish excretion and uneaten feed. Only about 30% of feed phosphorus and nitrogen are retained by salmonids, even if they consume all of the feed fed to them.
Commercial feeds are often formulated to contain a slightly higher level of a nutrient than is required by the species for maximum growth. The extra nutrients are added to feeds because few if any feed ingredients are completely digested and absorbed and so the extra nutrients serve as a safety margin to insure that requirements for maximum growth are met. Unfortunately, these safety margins contribute, in part, to the production of excess wastes in fish farm effluents.
As a result of these problems, the future of seafood as a significant component of the human diet is in serious doubt. Wild fisheries are in decline and are becoming increasingly polluted. Aquaculture, as it is practiced today, is not environmentally sound and does not offer a long-term sustainable solution.
Accordingly, the present invention has been developed in view of limitations, shortcomings and other disadvantages of conventional production practices.